Recently, micro electro mechanical systems (MEMS), such as machining silicon, etc. to form a micro element, etc have made enormous progress. Examples of the micromachined element formed by micro electro mechanical systems (MEMS) include an electrostatic actuator, such as a droplet discharging head (an ink jet head) used in a recording (printing) apparatus such as a droplet discharge type printer, a micro pump, an optical variable filter, and a motor, and a pressure sensor, etc.
On this occasion, a description will be given of the droplet discharging head as an electrostatic actuator, as an example of the micromachined element. Droplet discharge type recording (printing) apparatuses are used for printing in a whole range of fields including household use and industrial use. The droplet discharge type means, for example, moving a droplet discharging head having a plurality of nozzles relative to a target object (sheet, etc.), and then discharging droplets to the target object at a predetermined location to carry out printing, etc. This type is used in manufacturing color filters for producing display devices using liquid crystal, display panels using electroluminescence elements such as organic compounds (OLED), microarrays of biological molecule, such as DNAs, and protein substances, etc.
There exists a droplet discharging head of one type comprising a discharging chamber for storing liquid in part of a flow passage. According to this droplet discharging head, an inside of the discharging chamber is pressurized by deformation of at least one side wall (a bottom wall in this case, hereinafter referred to as diaphragm) of the discharging chamber caused by its deflection (operation) to permit the droplets to be discharged through nozzles communicated with the chamber. A force to displace the diaphragm as a movable electrode includes; for example, an electrostatic force (frequently an electrostatic attracting force) occurring between the diaphragm and an electrode (fixed electrode) opposed to the diaphragm with a distance.
In the above-mentioned electrostatic actuator utilizing an electrostatic force, charging the diaphragm and an individual electrode (opposed electrode) causes the diaphragm to be attracted and deflected toward the individual electrode. The diaphragm and the individual electrode maintain a predetermined gap (air gap, space) therebetween, so as to be arranged opposed to each other across this gap.
Generally, in electrostatic drive type ink jet recoding apparatuses, the gap between the diaphragm and the individual electrode is sealed by a sealing material. This aims to, for example, prevent an electrostatic attracting force and an electrostatic repulsive force from lowering by moisture adhered to a bottom surface of the diaphragm and a surface of the individual electrode. Further, this sealing material has also a function of preventing foreign substances, etc. from entering the gap.
In commonly used conventional electrostatic drive type ink jet heads, the gap is sealed by pouring an epoxy resin material, etc. into the gap between the diaphragm and the individual electrode.
In conventional ink jet heads and methods of manufacturing the same, an opening (communicating hole) of the gap between the diaphragm and the individual electrode is sealed by forming an oxide film thereon by a CVD (chemical vapor deposition) method, etc. (for example, refer to Patent Document 1)
Moreover, in conventional electrostatic actuators and ink jet heads using the same, the gap between the diaphragm and the individual electrode is sealed by using a silicon-containing polyimide family sealing material (for example, refer to Patent Document 2).
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-1972 (page 1, FIG. 1)
[Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-172790 (page 1, FIG. 1)